<html><head><title>Gives the GAIC for a GAMLSS Object</title>
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<table width="100%"><tr><td>IC(gamlss)</td><td align="right">R Documentation</td></tr></table><object type="application/x-oleobject" classid="clsid:1e2a7bd0-dab9-11d0-b93a-00c04fc99f9e">
<param name="keyword" value="R:   IC">
<param name="keyword" value="R:   AIC.gamlss">
<param name="keyword" value="R:   GAIC">
<param name="keyword" value="R:   extractAIC.gamlss">
<param name="keyword" value=" Gives the GAIC for a GAMLSS Object">
</object>


<h2>Gives the GAIC for a GAMLSS Object</h2>


<h3>Description</h3>

<p>
<code>IC</code> is a function to calculate the Generalized Akaike information criterion (GAIC) for a given penalty <code>k</code> for a fitted GAMLSS object. 
The function <code>AIC.gamlss</code> is the method associated with a GAMLSS object of the generic function <code>AIC</code>. 
The function <code>GAIC</code> is a synonymous of the function <code>AIC.gamlss</code>. 
The function <code>extractAIC</code> is a the method associated a GAMLSS object of the generic function <code>extractAIC</code> and it is 
mainly used in the <code>stepAIC</code> function.
</p>


<h3>Usage</h3>

<pre>
IC(object, k = 2)
## S3 method for class 'gamlss':
AIC(object, ..., k = 2)
GAIC(object, ..., k = 2 )
## S3 method for class 'gamlss':
extractAIC(fit, scale, k = 2, ...)
</pre>


<h3>Arguments</h3>

<table summary="R argblock">
<tr valign="top"><td><code>object</code></td>
<td>
an gamlss fitted model</td></tr>
<tr valign="top"><td><code>fit</code></td>
<td>
an gamlss fitted model</td></tr>
<tr valign="top"><td><code>...</code></td>
<td>
allows several GAMLSS object to be compared using a GAIC</td></tr>
<tr valign="top"><td><code>k</code></td>
<td>
the penalty with default <code>k=2.5</code></td></tr>
<tr valign="top"><td><code>scale</code></td>
<td>
this argument is not used in gamlss</td></tr>
</table>

<h3>Value</h3>

<p>
The function <code>IC</code> returns the GAIC for given penalty k of the GAMLSS object.
The function <code>AIC</code> returns a matrix contains the df's and the GAIC's for given penalty k. 
The function <code>GAIC</code> returns identical results to <code>AIC</code>. 
The function <code>extractAIC</code> returns vector of length two with the degrees of freedom and the AIC criterion.</p>

<h3>Author(s)</h3>

<p>
Mikis Stasinopoulos <a href="mailto:d.stasinopoulos@londonmet.ac.uk">d.stasinopoulos@londonmet.ac.uk</a>
</p>


<h3>References</h3>

<p>
Rigby, R. A. and  Stasinopoulos D. M. (2005). Generalized additive models for location, scale and shape,(with discussion), 
<EM>Appl. Statist.</EM>, <B>54</B>, part 3, pp 507-554.
</p>
<p>
Stasinopoulos D. M., Rigby R.A. and Akantziliotou C. (2006) Instructions on how to use the GAMLSS package in R.
Accompanying documentation in the current GAMLSS  help files, (see also  <a href="http://www.gamlss.com/">http://www.gamlss.com/</a>).
</p>
<p>
Stasinopoulos D. M. Rigby R.A. (2007) Generalized additive models for location scale and shape (GAMLSS) in R.
<EM>Journal of Statistical Software</EM>, Vol. <B>23</B>, Issue 7, Dec 2007, <a href="http://www.jstatsoft.org/v23/i07">http://www.jstatsoft.org/v23/i07</a>.
</p>


<h3>See Also</h3>

<p>
<code><a href="gamlss.html">gamlss</a></code>
</p>


<h3>Examples</h3>

<pre>
data(abdom)
mod1&lt;-gamlss(y~cs(x,df=3),sigma.fo=~cs(x,df=1),family=BCT, data=abdom)
IC(mod1)
mod2&lt;-gamlss(y~cs(x,df=3),sigma.fo=~x,family=BCT, data=abdom)
AIC(mod1,mod2,k=3)
GAIC(mod1,mod2,k=3)
extractAIC(mod1,k=3)
rm(mod1,mod2)
</pre>



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